The effects of imprisonment on criminal behavior are to be explored. This involves consideration of deterrence effects which are to be estimated statistically through improved econometric models and the effects of incapacitation, which are to be analyzed through stochastic process models. The effects of deterrence and incapacitation are to be integrated along with consideration of the effects of a "capacity constraint", which is a hypothesized limitation on the maximum amount of imprisonment that could be delivered. The research focuses on improved models of deterrent effects, using more homogeneous data, using more plausible identifications, and testing the sensitivity of the results to identification and by using longitudinal data to explore the possibility of recursive effects. Incapacitation effects are estimated by estimating the average individual crime rate based on criminal-history records, corrected for time served in prison. The existence of an imprisonment capacity constraint is tested by examining the time series of imprisonment rate in various States. An overall model is to be formulated and explored, partly for the relationships it might reveal, but also as an agenda for a total research program.